Starting fluids, such as ether, have long been used to aid in cold weather starting of internal combustion engines. Typically, liquid ether is injected into an inlet air stream, such as an intake manifold, where it vaporizes upon contact with the cold air. The air/ether charge is then combined with fuel during fuel injection into an engine combustion chamber. Ether lowers the temperature at which the mixture in the combustion chamber will ignite and thus shortens the ignition delay period. Engines usually run best when combustion begins before the piston reaches top dead center in the cylinder. Under cold start conditions without ether, ignition occurs late in the combustion cycle, or the combustible mixture may not ignite at all. Late ignition can cause a rapid rise in the cylinder pressure and result in serious engine damage. If one or more engine cylinders fails to ignite, the remaining cylinders carry an additional load which results in high pressures in the load-carrying cylinders. Engines are designed to operate below a maximum or peak pressure, and exceeding this limit can cause premature engine failure.
Typically, manual systems are used for starting fluid injection. More particularly, a vehicle operator simply uses an on/off switch to activate starting fluid injection whenever desired. Since these manual systems rely on operator activation, injection is highly unreliable and erratic. For example, it is possible for an excessive amount of starting fluid to be injected into an engine combustion chamber prior to engine cranking. If this occurs, serious engine damage can result when the combustible mixture ignites in the combustion chamber.
Several automatic systems have been developed to better control starting fluid injection. One such system is disclosed in U.S. Pat. No. 4,774,916 which issued on Feb. 11, 1987 to Smith. In Smith, a predetermined volume of starting fluid is repeatedly injected into an engine intake manifold during engine cranking. Injection of the starting fluid stops when the starter is no longer energized.
However, to eliminate white smoke from engine exhaust and to ensure smooth running during engine warm up, it is desirable to continue injection for a period of time after the engine starts. White smoke occurs when engine exhaust contains unburned fuel and it is both functionally and aesthetically desirable to eliminate white smoke from the engine exhaust. Injecting the starting fluid during this post-crank period lowers the flash point of the air/fuel mixture in the engine combustion chamber, thereby causing the fuel to burn more completely.
One injection system which provides this desirable post-cranking injection is disclosed in U.S. Pat. No. 4,202,309 which issued on July 20, 1978 to Burke. In Burke, starting fluid is continuously injected during engine cranking and a predetermined amount of fluid is subsequently injected from a reservoir when cranking ceases. Unfortunately, if an attempt to start the engine fails, the system still injects the predetermined amount when cranking stops. A subsequent attempt to start the engine can result in engine damage due to an excess amount of starting fluid in the combustion chamber. Furthermore, if the engine starts successfully, the volume of starting fluid subsequently injected is constant and therefore can be excessive or insufficient to solve the aforementioned problems.
The present invention is directed toward addressing the above mentioned problems by continuously injecting starting fluid during engine cranking and subsequently, after the engine starts, injecting starting fluid for a period of time based on one or more engine parameters. If the engine fails to start, injection ceases immediately thereby preventing excessive starting fluid injection. Other aspects, objects and advantages can be obtained from a study of the drawings, the disclosure, and the appended claims.